which is the strongest opening in chess

If there was a "strongest opening", why would any serious chess-player use any other opening?
1. Nf3. Is it to your taste?
I did play the KIA quite a bit... but really, the idea of a "strongest opening" seems rather simplistic.
Your goal in the opening is to reach an early-middle-game position in which you feel comfortable and confident. Whatever sequence of moves gets you there is the "best opening".
Grob is the worst opening: 1 g4? is the only first white move that loses by force.
And where are you getting that information from? Stockfish. As I have said not even stockfish could begin to unwrap the beauty that lies in the heart of the Grob opening. With optimal play white does not lose by force. Rather, white posses just enough counter-play to turn the tides and go into a fortress position, leading into an eventual draw.
The opposite-colored bishops with the queen and rook; a two-pawn advantage is actually doubled unsupported pawns, and the bishop is confined by its own pawns. Stockfish gives -2 but this position is actually a dead draw.